A tufted carpet is manufactured by using so-called tufts or tufting, i.e., a technique for producing three-dimensional surfaces which functions according to the principle of a sewing machine.
In this process, tufting needles introduce a tuft yarn into a base material, the so-called tuft backing. The tufting needles mounted on a needle bar are positioned along the width of the base material, a nonwoven fabric, for example, and simultaneously pierce through the base material. Before the tufting needles return upward to their starting position, the introduced tuft yarn is secured to the underside of the base material by grippers, referred to as loopers. This results in loops or slings, so-called neps, which form the visible side (top layer) of the finished carpet.
Depending on the application, these loops may be cut during the tufting process, using special blades. This results in the velour carpet, which is preferred in particular in the automotive interior sector, where it accounts for more than 95% of the total use.
Frequently used as tuft backing are nonwoven fabrics made of thermoplastic polymers, for example polyethylene terephthalate (PET) fibers and/or polypropylene (PP) fibers, which are bonded by needling, spot welding, by use of a chemical binder, by means of binding fibers, or a combination of these bonding processes.
The use of exclusively spot-welded or exclusively binder-bonded nonwoven fabrics is disadvantageous because these fabrics are not particularly well suited for production of three-dimensional shaped articles due to their poor deformability, especially for use in the automotive field.
When conventional round fibers are used, the contact surface and the friction between the fibers used in the nonwoven fabric tuft backing and the tuft yarns is relatively small, so that the retention force for the tuft yarn, in particular for complex carpet surface structures such as cut-loop velour or looped grades, or crossover velour grades (with offset pile knots), is frequently insufficient. The tuft yarn introduced into the tuft backing after penetration and withdrawal of the tufting needle may lose its intended position, i.e., the height or location of the nep, for example, as the result of the combination of slight variations in tuft backing density, yarn tension, and yarn quality, and in some cases the tuft yarn may even be pulled from the tuft backing. In both cases this may result in very noticeable defects and undesirable design flaws in the top layer of the tufted carpet.
The known conventional nonwoven fabrics having round fibers and used as tuft backing therefore do not meet the various requirements for particularly good adhesion of the tufted tuft yarns in the tuft backing, and are not always satisfactory for a defect-free tuft pattern in the top layer of the carpet.
It is known from U.S. Pat. No. 6,740,385 B2 that pattern uniformity and dimensional stability, in particular stability against deformation during and after the tufting process, may be improved by bringing tightly woven fabrics into contact with a uniform nonwoven fabric layer made of staple fibers and fusing them together.